In the mining and construction industries, loading and moving of heavy materials such as sand, gravel and rock is often accomplished using heavy machinery such as scoop trams, front-end loaders and powered bucket digging devices. During operation, these buckets tend to wear along their leading edges due to abrasion when entering the material pile and during contact with the ground. During use, the lip may tend to wear down, sometimes very quickly. After the lip wears down to a point where the base plate or bucket are threatened with wear, the bucket may typically be removed and sent to be refurbished by replacing the lip. Bucket removal is a relatively common practice in the mining industry at present. Rework and replacement of a bucket lip can be a major undertaking involving burning, cutting and welding. Time may be lost if the loader is transported to a shop where the bucket can be replaced. In a mining setting, the loader may remain inside the mine, the bucket being cut into two pieces and transported out of the mine to the surface. The replacement bucket may be returned in two pieces and be welded together before being placed on the loader. If a replacement bucket is not available or the replacement process is too cumbersome at the time, an operator may continue operating the loader nonetheless. As a result the base plate or the bucket itself may be damaged through overuse and may then require much more extensive repair than would otherwise be expected. The replacement of the base plate or bucket may well be much more costly than the use gained by operating the loader for the extra time.
Alternatively, the mine may keep an inventory of repaired buckets available. It is advantageous to reduce the ratio of buckets in inventory to the number of buckets in use, since buckets held in inventory, or being refurbished, are capital assets that are not earning revenue. Thus it is advantageous to make relatively simple replacement of wear plates and teeth in the mine, and to reduce the number of major overhauls requiring bucket removal to the surface.
When a loader or underground scoop tram is used for loading or transporting materials it is common to weld a base plate to the lower front edge of the bucket, the welding join line running from side to side across the bucket. The bucket is usually made of mild steel and the base plate is made of a mild steel or high carbon steel. The base plate is sometimes of greater thickness than the bucket plate. The upper surface of the base plate is installed flush with the inner surface of the bucket. The base plate has a lead, provided by leading edges that extend forwardly at an angle from the lower corners of the bucket to converge at a central point or tip. Different leads are selected by different operators to suit specific conditions. It is common for base plates to have leads of six, eight, ten or twelve inches, the lead being the distance that the tip is located forwardly of a line joining the outside corners of the bucket. A number of known scoop tram buckets have widths in the range of 56 to 112 inches, the tangent of the angle of the lead, viewed from above, being the lead dimension divided by the half width of the bucket.
Although the base plate can be more abrasion resistant than the material of the bucket, it is common practice to protect the base plate from premature wear by mounting a replaceable sacrificial wear lip or wear edge on the leading edges of the base plate. Typically, these wear edges are cut to suit, and are welded or bolted in place. Although welding and cutting operations tend to require greater labour they have been historically preferred. Releasable mechanical fastener systems, by contrast, tend to be regarded with considerable scepticism in view of the high stresses in the lip area during operation. However, mechanical fastening, as opposed to welding, permits different casting alloys to be used for the wear segments, and may tend to reduce reliance on specific welding skills to produce good welds in high wear alloys, such as, for example, Manganese steels.
It would also be advantageous to supply, and to bolt on, lip and wing wear segments that may be replaced several times over the life of the bucket. Some relatively complicated mechanical adapter systems are known, such as the Hensley (t.m.) J-bolt Edge System. This system uses a cleat that is welded to the bucket base plate, and a J-shaped bolt that attaches to the cleat to tighten a removable wear segment in place. The tightening action of the bolt is fore-and-aft, as opposed to vertical. The base plate does not have vertical bores for bolts. It would be advantageous to use a through-hole, as opposed to welded cleats. Leaving aside the lifting lug, the adapter fitting in the J-Bolt design stands up into the flow of incoming material a distance that is greater than the thickness of the base plate of the bucket. It would be preferable to employ fittings with a lower profile that may tend less to stand in the way of incoming material. In some replaceable wear equipment, the wear segments are bolted to the base plate by a dual flange fitting. This may result in looseness and high bolt stresses. It would be advantageous to use a single flange attachment.
The supply of replaceable wear edge assemblies for these wear areas, namely the forward lip and adjacent wing leading edges of excavating or loader buckets is the subject of this application, as is a system of standardisation that includes initial installation of base plate and wing segments, followed by the supply and installation of the remaining removable, and replaceable, wing and lip wear segments.
It is usual to weld a base plate along the lower edge of the bucket and to attach a cast, wear resistant lip along the leading edges of the base plate, as well as wing wear segments at the lower comers of the bucket. Usually, the base plate is welded to the bucket and the lip is welded to the base plate. The lip is usually made from a material, often as a casting, that is more wear resistant than the material used in the base plate or the bucket generally. For heavy digging the base plate and lip wear segments usually have a tapered or convergent lead, i.e., their front edges converge forwardly from the lower comers of the bucket, in some cases to a pointed tip as noted above, having an appearance of a pointed spade.
Loader buckets currently come in a variety of sizes. The present supplies of lip wear components to meet the numerous different bucket leads involves producing and stocking a wide variety of wear segments. As a result, many different sizes of lips may be manufactured and stocked to meet demand. This may result in a need to maintain a relatively large inventory. Another option is to sell one size of lips that can be trimmed by the user to match the bucket size. The rework of permanently installed (i.e., welded) wear components is also a major undertaking involving burning, cutting and welding. In many cases the work must be done in a heavy-duty garage. The lost machine operating time, the extent of the rework and the extra stocking of components may tend to be very costly and inefficient.
Replaceable, welded, leading edge wear shroud kits have been used in the past, but, in addition to the cutting and welding requirement, have tended to include elements as much as 40 inches wide or more. Such a part may weigh three hundred pounds or more. In general, the greater the weight of the part, the more difficult it is to handle, whether by hand or by machine, whether in shipping, transferring from one form of transport to another, installation or removal.
Further, the mating faces of the parts may not be planar, and may not be aligned with the forward and rearward direction of the bucket. Where the mating interfaces are arcuate or splayed, it may not necessarily be possible to remove each part without first removing another neighbouring part. The other part may not require replacement. This may complicate the occasional replacement of a single broken part, and may make general replacement of wear segments more time consuming than it need be. It would be advantageous to tend to avoid this complication by making the sides of adjoining segments straight and parallel, and preferably running in the fore-and-aft direction, to permit a segment to be slid into place between its neighbours. Although larger segments can be used, it would be advantageous to employ segments that are not more than 24 inches wide, and preferably not more than 20 inches wide. Similarly, it would be advantageous to keep the weight of each wear segment, or as many of them as practicable, below about 250 lbs., and preferably below about 200 lbs. It would also be preferable to be able to remove one segment without having to remove others first. That is, it would be advantageous to employ wear segments that do not require a specific order of removal and installation.
It would be advantageous, to adopt a wear plate system involving relatively few components, and relatively simple installation such as may be made in place with only minor lifting devices and bolting tools.
The effectiveness of a loader is determined by the number of loads per hour that can be loaded for a given material. Currently, lips for attachment to base plates have wedge shaped or rectangular profiles. These profiles may not be conducive to easy rolling of muck or other materials into the bucket. As a result, the effectiveness of the loader is reduced as muck gets caught on the lip or is slow to roll off the lip into the bucket. It may be advantageous to have a lip profile that may tend to encourage rolling motion in the muck. It may also be advantageous to have a lip profile in which the tip lies near or at the plane of the lower surface of the base plate.
It would be advantageous to have a lip that is mechanically attachable to, and removable from, the base plate relatively quickly and relatively easily, that is, without cutting, grinding or welding. It would be advantageous not to have to trim a cast or forged part to size for installation. It would also be advantageous if the shape of the lip were designed to encourage a rolling action in the material to be loaded. It would also be advantageous to use a method for providing lips which reduces inventory variety and inventory costs while still supporting a wide variety of bucket widths.
Accordingly, there is a need for a new lip design and a new method for providing such lips.